This invention relates to a printing apparatus, and more particularly to a thermal transfer type printing apparatus using a thermal head and thermal transfer ink.
A thermal transfer type printing apparatus reduced in size and weight dispenses with maintenance and so is widely used with, for example, a facsimile system or copying machine. With the conventional thermal transfer type printing apparatus so designed that an ink ribbon is pressed against a sheet of paper by a thermal head, an ink layer of the ink ribbon is transferred onto a paper surface in accordance with the contents of the print information received. The ink ribbon whose ink layer has already been transferred is taken up on a reel. However, the conventional thermal transfer type printing apparatus has the drawbacks that an ink ribbon taken up on a reel still retains an ink-removed portion corresponding to the print information received. This ink-removed portion remains visible as a negative, thereby enabling the print information to be read from the transferred ink ribbon, thus raising an important problem from the standpoint of keeping the secrecy of the print information.